The present invention relates to a screw compressor including a substantially cylindrical-shaped, vertical oil separator and an oil reservoir that accumulates an oil separated by the oil separator, and more particular, is suitable for a screw compressor that is used in a refrigerating cycle and reduces an oil flow-off quantity of the compressor (a quantity of oil flowing outside the compressor).
A screw compressor for use in, for example, a refrigerating cycle comprises a casing accommodating therein at least a pair of male and female rotors meshing with each other and bearings, a discharge casing including bearings supporting the male and female rotors, a substantially cylindrical-shaped, vertical oil separator, and an oil reservoir accumulating an oil separated by the oil separator.
Substantially cylindrical-shaped, vertical oil separators include a centrifugal-type oil separator, in which centrifugal forces induced by a swirling flow in a separation space adhere an oil to an inner wall surface and the oil revolves along the inner wall of the separator to descend and is accumulated in an oil reservoir (oil reserving space) provided in a lower portion of the separator. Further, the separator is generally structured so that gas is discharged from an upper portion of the separation space. As an example to separate and recover an oil contained in gas discharged from a compression mechanism part of a compressor by the centrifugal separation action, there is a separation system called a cyclone type disclosed in, for example, JP-A-2002-138980. This conventional example is constructed such that discharge gas of the compressor is introduced into a cyclone type oil separating chamber provided in an upper portion of an oil tank, the oil is primary separated by utilizing a centrifugal force, and then, as a measure of preventing the oil from being again scattered, minute oil mist is secondary separated by a mesh wire pad or the like.
As described in the JP-A-2002-138980, it is general in centrifugal separation type oil separators that a separation space and an oil reserving space are constructed to unite together.
As described above, while it is general in centrifugal separation type oil separators that a separation space and an oil reserving space are constructed to unite together, a distance (spatial distance above an oil surface) between an oil surface of an oil in an oil reservoir and a compressed gas discharge pipe inlet mounted in an upper portion of the oil separator must be made large in order to ensure a high separation efficiency, so that it is difficult to make the separator small in size.
On the other hand, in trying to make an oil separator small in size, the spatial distance above an oil surface must be reduced in order to ensure a necessary holding oil quantity, and in the case where the distance is made small, the oil is flung up from the oil surface when the gas flows into the discharge pipe, whereby there is caused a problem of a remarkable increase in oil flow-off quantity.
Also, as illustrated in the JP-A-2002-138980, it is general that an oil separator is constructed to unite with a discharge casing of a compressor. In overhauling the compressor, the work is performed with the discharge casing removed, but since the discharge casing is heavy, there is caused a problem that workability is worsened. Further, according to specifications, compressors are bound to mount thereon a safety device such as a safety valve, etc. but when a safety valve is mounted on a compressor, there is involved a disadvantage that a floor space occupied by the compressor is increased.
It is an object of the invention to provide a screw compressor that is simple in construction, can be made small in size, and can improve the workability at the time of overhaul operation.
It is another object of the invention to provide a screw compressor that can also reduce an oil flow-off quantity of the compressor (a quantity of oil flowing outside the compressor) while achieving miniaturization.
It is a further object of the invention to provide a screw compressor that can reduce a discharge casing in weight and can be made compact even when a safety device is mounted on the compressor.